Characterization of depositional conditions for lacustrine oil shales in the Eocene Jijuntun Formation, Fushun Basin, NE China

Abstract

The strike-slip Fushun Basin hosts a lacustrine oil shale interval of ca. 50-300 m in the Eocene (Lutetian) Jijuntun Formation. The oil shale deposits consist of the lower lean oil shale unit (LOSU) and the upper rich oil shale unit (ROSU). In outcrop areas, the identified depositional cycles of ca. 8-10 m and 5-8 m in thickness record the stacking of massive and non-laminated oil shales in the LOSU and fine-and coarse-laminated oil shales in the ROSU, respectively. Depositional conditions in the paleo-Jijuntun Lakes were synoptically reconstructed based on sedimentary features, trace element and organic geochemical proxies. Oxic to suboxic, freshwater conditions were prevailing in the paleo-Jijuntun Lakes during deposition of the LOSU, and then evolved into oxygen-deficient, fresh-to mildly brackish-water conditions during deposition of the ROSU, as revealed by the concentrations of redox-and salinity-sensitive trace elements (e.g. V/Ni, V/Cr, Ni/Co and Sr/Ba ratios, and boron content) in the oil shales. Warm to cool and humid to arid climate (represented by e.g. Sr/Cu and Rb/Sr ratios) could result in the deepening of water column (from ca. 20-30 m to ca. 100 m) and saline stratification superposed on pre-existing thermal stratification in the paleo-Jijuntun Lakes. A systematical decrease (approximately one order of

Geochemical Characteristics and Sedimentary Control of Pinghu Formation (Eocene) Coal‐bearing Source Rocks in Xihu Depression, East China Sea Basin

“…IH: Hydrogen Index = S2 × 100/TOC, mg /g TOC. 2015), Th/U (Wignall and Myers, 1988;Hatch and Leventhal, 1992;Jones and Manning, 1994;Xu et al, 2016), Ni/Co, V/Cr (Jones and Manning, 1994;Akinlua et al, 2010), and V/(V + Ni) (Jones and Manning, 1994;Xu et al, 2016;Zhao et al, 2016). The regionalization parameters ratio indicating oxidation-reduction conditions shows a fluctuating change vertically, which is consistent with the vertical variation trend of coal seam thickness (Figs.…”

Varves in the Yixian Formation, western Liaoning: Constraining the palaeoclimate in the Early Cretaceous

“…Based on the study of marine sediment, some redox‐sensitive elements (such as U, Th, V, Ni, Co and Cr) were used to reconstruct the redox environment (Hatch & Leventhal, 1992; Jones & Manning, 1994; Qiao, Liu, & Shang, 2019; Tan et al, 2019; F. Wang et al, 2017; S.‐C. Xu et al, 2016). D.‐H.…”

Geochemical Characteristics of the Middle Devonian Dacaozi-Tanshanping Shale Strata in the Yanyuan Basin, Southwest China: Implications for Organic Matter Accumulation and Preservation

“…Detailed analysis of the paleoredox conditions and further investigation of the paleoproductivity forcing mechanisms operating during sedimentation indicate that the shales of the Dacaozi and Tanshanping Formations were deposited under the controlling of paleoredox conditions. During the deposition period of the Dacaozi Formation, which was deposited in the more warm-humid shallow water environments, we found that significant increases in the temperature and humidity led to more fresh water inputs and a high degree of chemical weathering [79][80][81][82][83]. The higher terrigenous inputs, promoting abundant planktons and better condition of organic matter accumulation, coincides with the higher level of penetration from sunlight.…”